Vibrating device and image equipment having the same

ABSTRACT

A dust-screening member includes a plate-like light transmitting portion having a polygonal shape, and at least one plate-like side wall portion which tilts as much as a predetermined angle and extends from at least one side of the light transmitting portion so that they do not come in contact with each other. A vibrating member is fixed to one plate-like side wall portion and apples a vertical vibrational amplitude to the surface of the light transmitting portion. The light transmitting portion and the at least one side wall portion are formed to have a substantially uniform thickness by use of the same material. The light transmitting portion is positioned in front of an image forming element held by a holding member. The one side wall portion is fixed to the holding member at a position other than a position to which the vibrating member is fixed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2010-285926, filed Dec. 22, 2010,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to image equipment having image formingelements such as an image sensor element or a display element, and alsoto a vibrating device designed to vibrate the dust-screening member thatis arranged at the front of each image forming element of such an imageequipment.

2. Description of the Related Art

As image equipment having image forming elements, there is known animage acquisition apparatus that has an image sensor element configuredto produce a video signal corresponding to the light applied to itsphotoelectric conversion surface. Also known is an image projector thathas a display element, such as liquid crystal element, which displays animage on a screen. In recent years, image equipment having such imageforming elements have been remarkably improved in terms of imagequality. If dust adheres to the surface of the image forming elementsuch as the image sensor element or display element or to the surface ofthe transparent member (optical element) that is positioned in front ofthe image forming element, the image produced will have shadows of thedust particles. This makes a great problem.

For example, digital cameras of called “lens-exchangeable type” havebeen put to practical use, each comprising a camera body and aphotographic optical system removably attached to the camera body. Thelens-exchangeable digital camera is so designed that the user can usevarious kinds of photographic optical systems, by removing thephotographic optical system from the camera body and then attaching anyother desirable photographic optical system to the camera body. When thephotographic optical system is removed from the camera body, the dustfloating in the environment of the camera flows into the camera body,possibly adhering to the surface of the image sensor element or to thesurface of the transparent member (optical element), such as a lens,cover glass or the like, that is positioned in front of the image sensorelement. The camera body contains various mechanisms, such as a shutterand a diaphragm mechanism. As these mechanisms operate, they producedust, which may adhere to the surface of the image sensor element aswell.

Projectors have been put to practical use, too, each configured toenlarge an image displayed by a display element (e.g., CRT or liquidcrystal element) and project the image onto a screen so that theenlarged image may be viewed. In such a projector, too, dust may adhereto the surface of the display element or to the surface of thetransparent member (optical element), such as a lens, cover glass or thelike, that is positioned in front of the display element, and enlargedshadows of the dust particles may inevitably be projected to the screen.

Various types of mechanisms that remove dust from the surface of theimage forming element or the transparent member (optical element) thatis positioned in front of the image sensor element, provided in suchimage equipment have been developed.

In a vibrating device disclosed in, for example, US2008/0018775A1, anoptical low-pass filter constituted of first to third groups of opticalmembers, a piezoelectric element, an image acquisition element and thelike are incorporated in an image acquisition unit. That is, a vibrationtransmission member having a substantially L-shaped section is bondedand fixed to an upper side of the first group of optical members. Anurging force transmission member having a substantially L-shaped sectionis bonded and fixed to a facing lower side of the first group of opticalmembers. Moreover, a receiving portion for receiving the piezoelectricelement is formed in an upper side of a frame portion of a low-passfilter holding member which holds the low-pass filter. The piezoelectricelement has one end surface which is fixed to the frame portion with anadhesive or the like and held so that an expansion/contraction directiondue to the application of a voltage becomes an orthogonal direction (acamera upward/downward direction) with respect to an image acquisitionoptical axis. Furthermore, vibration in the orthogonal direction withrespect to the image acquisition optical axis is applied to the firstgroup of optical members as a dust-screening member by the piezoelectricelement, to remove foreign matters of dust and the like which adhere tothe surfaces of the optical members of the first group.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided avibrating device comprising:

a holding member configured to hold an image forming element having animage surface in which an optical image is generated;

a dust-screening member including a plate-like light transmittingportion which has a polygonal shape including a plurality of sides andis configured to permit the transmission of one of light coming from theimage forming element and light coming into the image forming element,and at least one plate-like side wall portion which tilts as much as apredetermined angle and extends from at least one side of the plate-likelight transmitting portion so that they do not come in contact with eachother; and

a vibrating member fixed to one plate-like side wall portion among theat least one plate-like side wall portion and configured to apply avertical vibrational amplitude to the surface of the plate-like lighttransmitting portion,

wherein the plate-like light transmitting portion and the at least oneplate-like side wall portion are formed to have a substantially uniformthickness by use of the same material,

the plate-like light transmitting portion is positioned in front of theimage forming element, and

the one plate-like side wall portion provided with the vibrating memberis fixed to the holding member at a position other than a position towhich the vibrating member is fixed.

According to another aspect of the present invention, there is providedan image equipment comprising:

an image forming element having an image surface in which an opticalimage is generated;

a holding member configured to hold the image forming element;

a dust-screening member including a plate-like light transmittingportion which has a polygonal shape including a plurality of sides andis configured to permit the transmission of one of light coming from theimage forming element and light coming into the image forming element,and at least one plate-like side wall portion which tilts as much as apredetermined angle and extends from at least one side of the plate-likelight transmitting portion so that they do not come in contact with eachother; and

a vibrating member fixed to one plate-like side wall portion among theat least one plate-like side wall portion and configured to apply avertical vibrational amplitude to the surface of the plate-like lighttransmitting portion,

wherein the plate-like light transmitting portion and the at least oneplate-like side wall portion are formed to have a substantially uniformthickness by use of the same material,

the plate-like light transmitting portion is positioned in front of theimage forming element, and

the one plate-like side wall portion provided with the vibrating memberis fixed to the holding member at a position other than a position towhich the vibrating member is fixed.

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. The advantages of the inventionmay be realized and obtained by means of the instrumentalities andcombinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a block diagram schematically showing an exemplary systemconfiguration, mainly electrical, of a digital camera that is a firstembodiment of the image equipment according to this invention;

FIG. 2A is a vertical side view of an image sensor element unit of thedigital camera, which includes a dust removal mechanism (or a sectionalview taken along line A-A shown in FIG. 2B);

FIG. 2B is a front view of the dust removal mechanism, as viewed fromthe lens side;

FIG. 3A is a perspective view showing a major component (vibrator) ofthe dust removal mechanism;

FIG. 3B is a sectional view of the major component, taken along line B-Bshown in FIG. 3A;

FIG. 3C is a sectional view of the major component, taken along line C-Cshown in FIG. 3A;

FIG. 4A is a front view of a dust filter, explaining how the dust filteris vibrated;

FIG. 4B is a sectional view of the dust filter, taken along line B-Bshown in FIG. 4A;

FIG. 4C is a sectional view of the dust filter, taken along line C-Cshown in FIG. 4A;

FIG. 5A is a front view of a dust filter, explaining how the dust filteris vibrated in another mode;

FIG. 5B is a sectional view of the dust filter, taken along line B-Bshown in FIG. 5A;

FIG. 5C is a sectional view of the dust filter, taken along line C-Cshown in FIG. 5A;

FIG. 6A is a perspective view showing another configuration the dustfilter may have;

FIG. 6B is a sectional view of the dust filter, taken along line B-Bshown in FIG. 6A;

FIG. 6C is a sectional view of the dust filter, taken along line C-Cshown in FIG. 6A;

FIG. 7 is a conceptual diagram of the dust filter, explaining thestanding wave that is produced in the dust filter;

FIG. 8 is a circuit diagram schematically showing the configuration of adust filter control circuit;

FIG. 9 is a timing chart showing the signals output from the componentsof the dust filter control circuit;

FIG. 10A is the first part of a flowchart showing an exemplary camerasequence (main routine) performed by the microcomputer for controllingthe digital camera body according to the first embodiment;

FIG. 10B is the second part of the flowchart showing the exemplarycamera sequence (main routine);

FIG. 11 is a flowchart showing the operating sequence of “silentvibration” that is a subroutine shown in FIG. 10A;

FIG. 12 is a flowchart showing the operation sequence of the “displayprocess” performed at the same time Step S201 of “silent vibration,”i.e. subroutine (FIG. 11), is performed;

FIG. 13 is a flowchart showing the operating sequence of the “displayprocess” performed at the same time Step S203 of “silent vibration,”i.e., or subroutine (FIG. 11), is performed;

FIG. 14 is a flowchart showing the operating sequence of the “displayprocess” performed at the same time Step S205 of “silent vibration,”i.e., subroutine (FIG. 11), is performed;

FIG. 15 is a diagram showing the form of a resonance-frequency wavecontinuously supplied to vibrating members during silent vibration; and

FIG. 16 is a flowchart showing the operating sequence of “silentvibration,” i.e., subroutine in the operating sequence of the digitalcamera that is a second embodiment of the image equipment according tothe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Best modes of practicing this invention will be described with referenceto the accompanying drawings.

First Embodiment

An image equipment according to this invention, which will beexemplified below in detail, has a dust removal mechanism for the imagesensor element unit that performs photoelectric conversion to produce animage signal. Here, a technique of improving the dust removal functionof, for example, an electronic camera (hereinafter called “camera” willbe explained. The first embodiment will be described, particularly inconnection with a lens-exchangeable electronic camera (digital camera),with reference to FIGS. 1 to 2B.

First, the system configuration of a digital camera 10 according to thisembodiment will be described with reference to FIG. 1. The digitalcamera 10 has a system configuration that comprises body unit 100 usedas camera body, and a lens unit 200 used as an exchange lens, i.e., oneof accessory devices.

The lens unit 200 can be attached to and detached from the body unit 100via a lens mount (not shown) provided on the front of the body unit 100.The control of the lens unit 200 is performed by the lens-controlmicrocomputer (hereinafter called “Lucom”) 201 provided in the lens unit200. The control of the body unit 100 is performed by the body-controlmicrocomputer (hereinafter called “Bucom” 101 provided in the body unit100. By a communication connector 102, the Lucom 210 and the Bucom 101are electrically connected to each other, communicating with each other,while the lens unit 200 remains attached to the body unit 100. The Lucom201 is configured to cooperate, as subordinate unit, with the Bucom 101.

The lens unit 200 further has a photographic lens 202, a diaphragm 203,a lens drive mechanism 204, and a diaphragm drive mechanism 205. Thephotographic lens 202 is driven by a stepping motor (not shown) that isprovided in the lens drive mechanism 204. The diaphragm 203 is driven bya stepping motor (not shown) that is provided in the diaphragm drivemechanism 205. The Lucom 201 controls these motors in accordance withthe instructions made by the Bucom 101.

In the body unit 100, a shutter 108, a shutter cocking mechanism 112,and a shutter control circuit 113 are arranged as shown in FIG. 1. Theshutter 108 is a focal plane shutter arranged on the photographicoptical axis. The shutter cocking mechanism 112 biases the spring (notshown) that drives the front curtain and rear curtain of the shutter108. The shutter control circuit 113 controls the motions of the frontcurtain and rear curtain of the shutter 108.

In the body unit 100, an image acquisition unit 116 is further providedalong a photographic optical axis to perform photoelectric conversion onthe image of an object, which has passed through the above-mentionedoptical system. The image acquisition unit 116 is constituted as a unitby integrating an image forming unit and a dust filter 119 which is adust-screening member, via a holder 145. The image forming unit includesa CCD 117 that is an image sensor element as an image forming elementhaving an image surface in which an optical image is generated, and anoptical low-pass filter (LPF) 118 that is arranged in front of the CCD117. Here, the optical low-pass filter (LPF) 118 is an optical elementmade of quartz crystal or the like. The dust filter 119 is an opticalelement made of quartz crystal, glass or the like, and may be made of atransparent plastic material. That is, the dust filter 119 is preferablya transparent member which can form a configuration having, for example,an L-shaped section as described later in detail and which can bevibrated.

On one side of the circumferential edge of the dust filter 119, apiezoelectric element 120 is attached. The piezoelectric element 120 hastwo electrodes. A dust filter control circuit 121, which is a driveunit, drives the piezoelectric element 120 at the frequency determinedby the size and material of the dust filter 119. As the piezoelectricelement 120 vibrates, the dust filter 119 undergoes specific vibration.Dust can thereby be removed from the surface of the dust filter 119. Tothe image acquisition unit 116, an anti-vibration unit is attached tocompensate for the motion of the hand holding the digital camera 10.

The digital camera 10 according to this embodiment further has a CCDinterface circuit 122, a liquid crystal monitor 123, an SDRAM 124, aFlash ROM 125, and an image process controller 126, thereby to performnot only an electronic image acquisition function, but also anelectronic record/display function. The electronic image acquisitionfunction includes a so-called through image display function, whichdisplays an image acquired by the CCD 117 as a moving image on theliquid crystal monitor 123, and uses it as a viewfinder, and a movingimage recording function which records a moving image. As a viewfinderfunction, an optical single-lens reflex viewfinder or the like may beprovided. The CCD interface circuit 122 is connected to the CCD 117. TheSDRAM 124 and the Flash ROM 125 function as storage areas. The imageprocess controller 126 uses the SDRAM 124 and the Flash ROM 125, toprocess image data. A recording medium 127 is removably connected by acommunication connector (not shown) to the body unit 100 and cantherefore communicate with the body unit 100. The recording medium 127is an external recording medium, such as one of various memory cards oran external HDD, and records the image data acquired by photography. Asanother storage area, a nonvolatile memory 128, e.g., EEPROM, isprovided and can be accessed from the Bucom 101. The nonvolatile memory128 stores prescribed control parameters that are necessary for thecamera control.

To the Bucom 101, there are connected an operation display LCD 129, anoperation display LED 130, a camera operation switch 131, and a flashcontrol circuit 132. The operation display LCD 129 and the operationdisplay LED 130 display the operation state of the digital camera 10,informing the user of this operation state. The operation display LED129 or the operation display LED 130 has, for example, a display unitconfigured to display the vibration state of the dust filter 119 as longas the dust filter control circuit 121 keeps operating. The cameraoperation switch 131 is a group of switches including, for example, arelease switch, a mode changing switch, a power switch, which arenecessary for the user to operate the digital camera 10. The flashcontrol circuit 132 drives a flash tube 133.

In the body unit 100, a battery 134 used as power supply and apower-supply circuit 135 are further provided. The power-supply circuit135 converts the voltage of the battery 134 to a voltage required ineach circuit unit of the digital camera 10 and supplies the convertedvoltage to the each circuit unit. In the body unit 100, too, a voltagedetecting circuit (not shown) is provided, which detects a voltagechange at the time when a current is supplied from an external powersupply though a jack (not shown).

The components of the digital camera 10 configured as described aboveoperate as will be explained below. The image process controller 126controls the CCD interface circuit 122 in accordance with theinstructions coming from the Bucom 101, whereby image data is acquiredfrom the CCD 117. The image data is converted to a video signal by theimage process controller 126. The image represented by the video signalis displayed by the liquid crystal monitor 123. Viewing the imagedisplayed on the liquid crystal monitor 123, the user can confirm theimage photographed.

The SDRAM 124 is a memory for temporarily store the image data and isused as a work area in the process of converting the image data. Theimage data is held in the recording medium 127, for example, after ithas been converted to JPEG data. Here, when image data is for a movingimage, it is converted into MPEG data.

The photographic lens 202 is focused as follows. Images are acquired bysequentially changing the position of the photographic lens 202. Amongthe acquired images, a position with the highest contrast is calculatedby the Bucom 101. This position is transmitted from the Bucom 101 to theLucom 201 through the communication connector 102. The Lucom 201controls the photographic lens 202 to this position. As for photometricmeasurement, know measurement is performed based on the amount of lightdetected from an acquired image.

The image acquisition unit 116 that includes the CCD 117 will bedescribed with reference to FIGS. 2A and 2B. Note that the hatched partsshown in FIG. 2B show the shapes of members clearly, not to illustratingthe sections thereof.

As described above, the image acquisition unit 116 has the CCD 117, theoptical LPF 118, the dust filter 119, and the piezoelectric element 120.The CCD 117 is an image sensor element that produces an image signalthat corresponds to the light applied to its photoelectric conversionsurface through the photographic optical system. The optical LPF 118 isarranged at the photoelectric conversion surface of the CCD 117 andremoves high-frequency components from the light beam coming from theobject through the photographic optical system. The dust filter 119 is adust-screening member having the L-shaped section which is arranged infront of this optical LPF 118 so as to face the optical LPF 118, spacedapart therefrom by a predetermined distance. The piezoelectric element120 is arranged on a side wall portion of the dust filter 119 and is avibrating member for applying specific vibration to the dust filter 119.

The CCD chip 136 of the CCD 117 is mounted directly on a flexiblesubstrate 137 that is arranged on a fixed plate 138. From the ends ofthe flexible substrate 137, connection parts 139 a and 139 b extend.Connectors 140 a and 140 b are provided on a main circuit board 141. Theconnection parts 139 a and 139 b are connected to the connectors 140 aand 140 b, whereby the flexible substrate 137 is connected to the maincircuit board 141. The CCD 117 has a protection glass plate 142. Theprotection glass plate 142 is secured to the flexible substrate 137,with a spacer 143 interposed between it and the flexible substrate 137.

Between the CCD 117 and the optical LPF 118, a filter holding member 144made of elastic material is arranged on the front circumferential edgeof the CCD 117, at a position where it does not cover the effective areaof the photoelectric conversion surface of the CCD 117. The filterholding member 144 abuts on the optical LPF 118, at a part close to therear circumferential edge of the optical LPF 118. The filter holdingmember 144 functions as a sealing member that maintains the junctionbetween the CCD 117 and the optical LPF 118 almost airtight. A holder145 is provided, covering seals the CCD 117 and the optical LPF 118 inairtight fashion. The holder 145 has a rectangular opening 146 in a partthat is substantially central around the photographic optical axis. Theinner circumferential edge of the opening 146, which faces the dustfilter 119, has a stepped part 147 having an L-shaped cross section. Theoptical LPF 118 and a CCD 117 are arranged in the opening 146 from arear side thereof, to form a holding member which holds the CCD 117. Inthis case, the front circumferential edge of the optical LPF 118contacts the stepped part 147 in a virtually airtight fashion. Thus, theoptical LPF 118 is held by the stepped part 147 at a specific positionin the direction of the photographic optical axis. The optical LPF 118is therefore prevented from slipping forwards from the holder 145. Thelevel of airtight sealing between the CCD 117 and the optical LPF 118 issufficient to prevent dust from entering to form an image having shadowsof dust particles. In other words, the sealing level need not be so highas to completely prevent the in-flow of gasses.

On the other hand, a front surface side of the holder 145 is providedwith an opening which becomes an image forming light passing area 149. Areceiving member 150 is formed into an annular shape to surround theopening in front of the holder 145. The receiving member 150 holds thedust filter 119 in front of the optical LPF 118 via a predeterminedspace therefrom, and is made of an elastic material such as a rubber ora resin having vibration attenuating properties. The dust filter 119having the L-shaped section includes a plate-like bottom surface portion119 a and a plate-like side wall portion 119 b, and the bottom surfaceportion 119 a is held by the receiving member 150. The bottom surfaceportion 119 a is a plate-like light transmitting portion having apolygonal shape, to permit the transmission of light coming into the CCD117. The side wall portion 119 b tilts as much as a predetermined angle(here, substantially 90°) and extends from one side of the bottomsurface portion 119 a having the polygonal shape so that the portions donot come in contact with each other. The side wall portion 119 b isfixed to a peripheral edge of the opening of the holder 145 by afastening member 151 such as a screw. In this case, the bottom surfaceportion 119 a is fixed to be supported by the receiving member 150 in apredetermined pressing state. The one side of the bottom surface portion119 a from which the side wall portion 119 b does not extend forms afree end.

The receiving member 150 is made of an elastic material such as a rubberor a resin having the vibration attenuating properties, not to impedethe vibration of the dust filter 119. Moreover, a space formed by thedust filter 119 and the LPF 118 is sealed from the dust, because thereceiving member 150 is deformed in accordance with a vibrating state ofthe dust filter 119, and hence such dust that forms an image havingshadows of dust particles does not enter this space from the outside.The holder 145 formed in a desired size to mount the CCD 117 as an imageforming element thereon, the receiving member 150, and the filterholding member 144 which airtightly holds betweenness of the CCD 117 andthe optical LPF 118 constitute a sealing structure to seal at thecircumferential edges of the CCD 117 and dust filter 119. The imageacquisition unit 116 is configured, so that the area formed by theopposing CCD 117 and dust filter 119 is airtight by the above sealingstructure. The level of airtight sealing between the dust filter 119 andthe receiving member 150 is sufficient to prevent dust from entering toform an image having the shadows of dust particles, so that the imagecan be prevented from being influenced by the dust. The sealing levelneed not be so high as to completely prevent the in-flow of gasses.

To the end of the piezoelectric element 120, which is vibrating member,flex 157, i.e., flexible printed board, is electrically connected. Theflex 157 inputs an electric signal (later described) from the dustfilter control circuit 121 to the piezoelectric element 120, causing theelement 120 to vibrate in a specific way. The flex 157 is made of resinand cupper etc., and has flexibility. Therefore, the flex 157 littleattenuates the vibration of the piezoelectric element 120. The flex 157is provided at position where the vibrational amplitude is small (at thenodes of vibration, which will be described later), and can thereforesuppress the attenuation of vibration. The piezoelectric element 120moves relative to the body unit 100 if the camera 10 has such ahand-motion compensating mechanism as will be later described. Hence, ifthe dust filter control circuit 121 is held by a holding member formedintegral with the body unit 100, the flex 157 is deformed and displacedas the hand-motion compensating mechanism operates. In this case, theflex 157 effectively works because it is thin and flexible. In thepresent embodiment, the flex 157 has a simple configuration, extendingfrom one position. It is best fit for use in cameras having ahand-motion compensating mechanism.

The dust removed from the surface of the dust filter 119 falls onto thebottom of the body unit 100, by virtue of the vibration inertia and thegravity. In this embodiment, a base 158 is arranged right below the dustfilter 119, and a holding member 159 made of, for example, adhesivetape, is provided on the base 158. The holding member 159 reliably trapsthe dust fallen from the dust filter 119, preventing the dust frommoving back to the surface of the dust filter 119.

The hand-motion compensating mechanism will be explained in brief. Asshown in FIG. 1, the hand-motion compensating mechanism is composed ofan X-axis gyro 160, a Y-axis gyro 161, a vibration control circuit 162,an X-axis actuator 163, a Y-axis actuator 164, an X-frame 165, a Y-frame166 (holder 145), a frame 167, a position sensor 168, and an actuatordrive circuit 169. The X-axis gyro 160 detects the angular velocity ofthe camera when the camera moves, rotating around the X axis. The Y-axisgyro 161 detects the angular velocity of the camera when the camerarotates around the Y axis. The vibration control circuit 162 calculatesa value by which to compensate the hand motion, from theangular-velocity signals output from the X-axis gyro 160 and Y-axis gyro161. In accordance with the hand-motion compensating value thuscalculated, the actuator drive circuit 169 moves the CCD 117 in theX-axis direction and Y-axis direction, which are first and seconddirections orthogonal to each other in the XY plane that isperpendicular to the photographic optical axis, thereby to compensatethe hand motion, if the photographic optical axis is taken as Z axis.More precisely, the X-axis actuator 163 drives the X-frame 165 in theX-axis direction upon receiving a drive signal from the actuator drivecircuit 169, and the Y-axis actuator 164 drives the Y-frame 166 in theY-axis direction upon receiving a drive signal from the actuator drivecircuit 169. That is, the X-axis actuator 163 and the Y-axis actuator164 are used as drive sources, the X-frame 165 and the Y-frame 166(holder 145) which holds the CCD 117 of the image acquisition unit 116are used as objects that are moved with respect to the frame 167. Notethat the X-axis actuator 163 and the Y-axis actuator 164 are eachcomposed of an electromagnetic motor, a feed screw mechanism, and thelike. Alternatively, each actuator may be a linear motor using a voicecoil motor, a linear piezoelectric motor or the like. The positionsensor 168 detects the position of the X-frame 165 and the position ofthe Y-frame 166. On the basis of the positions the position sensor 168have detected, the vibration control circuit 162 controls the actuatordrive circuit 169, which drives the X-axis actuator 163 and the Y-axisactuator 164. The position of the CCD 117 is thereby controlled.

The dust removal mechanism of the first embodiment will be described indetail, with reference to FIGS. 3A to 7. The dust filter 119 has theL-shaped section as shown in FIG. 3A. A bottom surface portion 119 a ofthe dust filter 119 has a shape surrounded by a curve including acircle, or a polygonal plate-like shape as a whole (a square plate, inthis embodiment). Moreover, in the bottom surface portion 119 a of thedust filter 119, at least, the area spreading as prescribed from theposition obtaining a maximum vibrational amplitude to the radialdirection forms a light transmitting part. Alternatively, the bottomsurface portion 119 a of the dust filter 119 has a circular shape as awhole, and may be D-shaped, formed by linearly cutting part of acircular plate, thus defining one side. Still alternatively, it may beformed in an oval shape by cutting a square plate, having two oppositesides accurately cut and having upper and lower sides. In this manner,the shape may be a combination of curves and straight lines. Moreover,the dust filter 119 includes the side wall portion 119 b which tilts asmuch as a predetermined angle and extends from at least one side of thebottom surface portion 119 a and from an end surface portion of the oneside thereof in FIG. 3A in a direction of the CCD 117 so that they donot come in contact with each other. The side wall portion 119 b has arectangular shape formed by the one side of the plate-like bottomsurface portion 119 a and a side which is shorter than the one side ofthe plate-like bottom surface portion 119 a. Moreover, the side wallportion 119 b is fixed to the holder 145 by the fastening member 151 sothat the light transmitting portion of the dust filter 119 is arrangedin front of the optical LPF 118 to face the optical LPF via apredetermined space therefrom. Here, the bottom surface portion 119 aand the side wall portion 119 b of the dust filter 119 having theL-shaped section are formed to have a substantially uniform thickness byuse of the same material.

Moreover, the piezoelectric element 120 is fixed to the side wallportion 119 b of the dust filter 119 by means of, for example, adhesionusing the adhesive, or the like. The piezoelectric element 120 is avibrating member for applying a vertical vibrational amplitude to thesurface of the bottom surface portion 119 a which is the lighttransmitting portion of the dust filter 119. It is to be noted that thepiezoelectric element 120 has a rectangular shape, and the piezoelectricelement 120 is arranged to be received in the side wall portion 119 b.Furthermore, the side wall portion 119 b is fixed to the holder 145 bythe fastening member 151 at a position other than a position to whichthe piezoelectric element 120 is fixed. In consequence, a vibrator 170is formed by arranging the piezoelectric element 120 on the dust filter119. The vibrator 170 undergoes resonance when a voltage of a prescribedfrequency is applied to the piezoelectric element 120. The resonanceachieves such bending vibration of a large amplitude vertically to thebottom surface portion 119 a, as illustrated in FIG. 4A to FIG. 4C.

Here, an angle formed by the each side wall portion 119 b and the bottomsurface portion 119 a as a light transmitting portion constituting thedust filter 119 is preferably 90° or more, when the integral forming ofthe side wall portion 119 b and the bottom surface portion 119 a istaken into consideration. Moreover, when the enlargement of a projectedarea and the rigidity are taken into consideration, the angle ispreferably set to be about 135° or less. Furthermore, when a surfaceconnecting the bottom surface portion 119 a to the side wall portion 119b is constituted of a surface which is approximate to a cylindricalsurface as shown in FIG. 3A and FIG. 3B, the rigidity of the dust filter119 becomes higher, and the dust filter 119 can be miniaturized. Inother words, the side wall portion 119 b has a high rigidity in anoptical axis direction and is not deformed, whereas the bottom surfaceportion 119 a which is the light transmitting portion can freely bend asa cantilever. In consequence, there can be provided a small-sizedvibrator 170 in which an attachment structure of the dust filter 119 andthe piezoelectric element 120 is simple and whose performance is notimpaired even if the attachment structure is simple and which cangenerate a desirable vibration waveform in the dust filter 119.

As shown in FIG. 3A, signal electrodes 171 and 172 are formed on thepiezoelectric element 120. Note that the hatched parts shown in FIG. 3Ashow the shapes of the signal electrodes clearly, not to illustratingthe sections thereof. The signal electrode 172 is provided on the backopposing the signal electrode 171, and is bent toward that surface ofthe piezoelectric element 120, on which the signal electrode 171 isprovided, along the side wall portion of the piezoelectric element 120.The flex 157 having the above-mentioned conductive pattern iselectrically connected to the signal electrode 171 and signal electrode172. To the signal electrodes 171 and 172, a drive voltage of theprescribed frequency is applied form the dust filter control circuit 121through flex 157. The drive voltage, thus applied, can cause the dustfilter 119 to undergo such a two-dimensional, standing-wave bendingvibration as is shown in FIGS. 4A to 4C. The side wall portion 119 b ofthe dust filter 119 has a long side length LA, and a short side lengthLB orthogonal to the long side. Since the dust filter 119 shown in FIG.4A is rectangular, it is identical in shape to the “virtual rectangle”according to this invention (described later). (The long side length LAis equal to the side length LF of the virtual rectangle). The bendingvibration shown in FIG. 4A is standing wave vibration. In FIG. 4A, theblacker the streaks, each indicating a node area 173 of vibration (i.e.,area where the vibrational amplitude is small), the smaller thevibrational amplitude is. Note that the meshes shown in FIG. 4A aredivision meshes usually used in the final element method.

If the node areas 173 are at short intervals as shown in FIG. 4A whenthe vibration speed is high, in-plane vibration (vibration along thesurface) will occur in the node areas 173. This vibration induces alarge inertial force in the direction of the in-plane vibration (seemass point Y2 in FIG. 7, described later, which moves over the nodealong an arc around the node, between positions Y2 and Y2′) to the dustat the node areas 173. If the dust filter 119 is inclined to becomeparallel to the gravity so that a force may act along the dust receivingsurface, the inertial force and the gravity can remove the dust from thenode areas 173.

In FIG. 4A, the white areas indicate areas where the vibrationalamplitude is large. The dust adhering to any white area is removed bythe inertial force exerted by the vibration. The dust adhering to a nodearea 173 of the vibration can be removed, when an electric signal havinga different frequency is input into the piezoelectric element 120 toproduce vibration in another vibration mode with another vibrationalamplitude in the node area 173 (e.g. a vibrational mode shown in FIG.5A).

The bending vibrational mode shown in FIG. 4A is achieved bysynthesizing the bending vibration of the X-direction and the bendingvibration of the Y-direction. A vibrational mode with a very largevibrational amplitude can be obtained, even if a piezoelectric elementis placed along one side as in this embodiment. (The maximum amplitudeat the same level as at the conventional circular dust filter isgenerated.) At this time, the vibrational mode will be the mode shown inFIG. 4A is obtained. In this vibrational mode, peak ridges of thevibrational amplitude continuously positioned in a substantiallyconcentric shape are formed from one side symmetric to a first virtualaxis VL1 passing through a centroid 119 c of the dust filter 119 to theother side arranged to face the one side, and a reflected wave comingfrom a side extending in an X-direction and a reflected wave coming froma side extending in a Y-direction are efficiently combined, to form astanding wave. Here, one side of the piezoelectric element 120 in alongitudinal direction thereof is arranged substantially in parallelwith one side of the bottom surface portion 119 a which is the lighttransmitting portion of the dust filter 119 so that a centroid of thepiezoelectric element 120 is located on the first virtual axis VL1.Moreover, a centroid 175 a of a central vibrating area 175 having thehighest vibration speed and the largest vibrational amplitude and thecentroid 119 c of the dust filter 119 are similarly located on the firstvirtual axis VL1. That is, the first virtual axis VL1 connecting amidpoint of the one side of the piezoelectric element 120 in thelongitudinal direction to a midpoint (the centroid 119 c of the dustfilter 119) of one side of the bottom surface portion 119 a which is aplate-like light transmitting portion corresponding to the image forminglight passing area 149 matches a second virtual axis VL2 connecting avibration center (the centroid 175 a of the central vibrating area 175)of the bottom surface portion 119 a which is the plate-like lighttransmitting portion to the midpoint (the centroid 119 c of the dustfilter 119) of the one side of the plate-like bottom surface portion 119a. However, since only one piezoelectric element 120 is disposed, thecentroid 175 a of the central vibrating area 175 is displaced from thecentroid 119 c of the dust filter 119 to a side provided with thepiezoelectric element 120.

Here, the centroid of the piezoelectric element 120 does not expand orcontract, even if a driving voltage is applied, and hence thepiezoelectric element 120 is preferably attached so that the centroidthereof is positioned in the node area. On the other hand, since theside wall portion 119 b of the dust filter 119 extends in a direction ofthe amplitude of the generated vibration, a boundary portion between thebottom surface portion 119 a and the side wall portion 119 b on thefirst virtual axis VL1 does not vibrate but forms the node area 173.Therefore, the piezoelectric element 120 has the centroid thereofdisposed in the above boundary portion on the first virtual axis VL1. Inthis case, when the piezoelectric element 120 is disposed on the bottomsurface portion 119 a of the dust filter 119, the position of thecentroid becomes a position where the vibrational amplitude becomeslarge to a certain degree, even if the element is disposed along a longside in the above boundary portion. This is because the piezoelectricelement 120 has a certain degree of dimension in a short side directionthereof. On the other hand, when the piezoelectric element 120 isdisposed on the side wall portion 119 b of the dust filter 119, theposition of the centroid preferably substantially corresponds to theabove boundary portion, because the piezoelectric element 120 has asmall dimension in a thickness direction.

The dust filter 119 of the vibrator 170, shown in FIGS. 4A to 4C, is aglass plate (optical element) having a size of 25.0 mm (X-direction: LA,LF)×24.2 mm (Y-direction: LB)×4.2 mm (Z-direction: H), and including thebottom surface portion 119 a and the side wall portion 119 b each havinga uniform thickness of 0.2 mm. The piezoelectric element 120 is made ofa lead titanate-zirconate ceramic and has a size of 16.6 mm(X-direction)×2.4 mm (Y-direction)×0.6 mm (thickness). The piezoelectricelement 120 is adhered with epoxy-based adhesive to the dust filter 119,extending along the side wall portion 119 b. More specifically, thepiezoelectric element 120 extends in the X-direction, and arrangedsymmetric in the Z-direction, with respect to an axis which is parallelto the X-axis passing through the center of the side wall portion of thedust filter 119 and an axis which is parallel to the Z-axis. At thistime, the resonance frequency in the vibrational mode of FIG. 4A is inthe vicinity of 90 kHz. At the center of the dust filter 119, thecentral vibrating area 175 having maximal vibration speed andvibrational amplitude can be attained if the dust filter is shaped likea circle in which the rectangular dust filter 119 is inscribed.

Moreover, a vibrational mode of FIG. 5A to FIG. 5C is a mode generatedby changing a vibrating frequency (for example, about 78 kHz) of thedust filter 119 shown in FIG. 4A to FIG. 4C.

In still another modification of a vibrator 170 shown in FIG. 6A to FIG.6C, side wall portions 119 b extend respectively from one of sides,which face each other, of a bottom surface portion 119 a which is arectangular light transmitting portion of a dust filter 119, to form thedust filter 119 having a U-shaped section as a whole. Moreover, apiezoelectric element 120 is provided on one of the two side wallportions 119 b. The other sides of the bottom surface portion 119 a fromwhich the side wall portions 119 b do not extend form free ends,respectively. In consequence, the bottom surface portion 119 a which isthe light transmitting portion can freely bend as a both supporting endbeam. Therefore, there can be provided a small-sized vibrator 170 inwhich an attachment structure of the dust filter 119 and thepiezoelectric element 120 is simple and whose performance is notimpaired even if the attachment structure is simple and which cangenerate a desirable vibration waveform in the dust filter 119.Moreover, in such a constitution, portions of the dust filter 119 whichface via the holder 145 are fixed to the holder 145 by fastening members151, and hence the dust filter has substantially higher airtightnessthan the dust filter 119 having an L-shaped section.

Note that it has been described that a material of the dust filter 119is transparent glass, but the material may be a resin such as amethacrylic methyl resin or a polycarbonate resin. A resin or glassmaterial which enables forming is optimum.

A method of removing dust will be explained in detail, with reference toFIG. 7. FIG. 7 shows a cross section identical to that shown in FIG. 4B.Assume that the piezoelectric element 120 is polarized in the directionof arrow 177 as shown in FIG. 7. If a voltage of a specific frequency isapplied to the piezoelectric element 120 at a certain time t₀, thevibrator 170 will be deformed as indicated by solid lines. At the masspoint Y existing at given position y in the surface of the vibrator 170,the vibration z in the Z-direction is expressed by Equation 1, asfollows:z=A·sin(Y)·cos(ωt)  (1)where ω is the angular velocity of vibration, A is the amplitude ofvibration in the Z-direction, and Y=2πy/λ (λ: wavelength of bendingvibration).

The Equation 1 represents the standing-wave vibration shown in FIG. 4A.Thus, if y=s·λ/2 (here, is an integer), then Y=sπ, and sin(Y)=0. Hence,a node 178, at which the amplitude of vibration in the Z-direction iszero irrespective of time, exists for every n/2. This is standing-wavevibration. The state indicated by broken lines in FIG. 7 takes place ift=kπ/ω (k is odd), where the vibration assumes a phase opposite to thephase at time t₀.

Vibration z(Y₁) at point Y₁ on the dust filter 119 is located at anantinode 179 of standing wave, bending vibration. Hence, the vibrationin the Z-direction has amplitude A, as expressed in Equation 2, asfollows:z(Y ₁)=A·cos(ωt)  (2)

If Equation 2 is differentiated with time, the vibration speed Vz(Y₁) atpoint Y₁ is expressed by Equation 3, below, because ω=2πf, where f isthe frequency of vibration:

$\begin{matrix}{{{Vz}( Y_{1} )} = {\frac{\mathbb{d}( {z( Y_{1} )} )}{\mathbb{d}t} = {{- 2}\;\pi\;{f \cdot A \cdot {\sin( {\omega\; t} )}}}}} & (3)\end{matrix}$If Equation 3 is differentiated with time, vibration acceleration αz(Y₁)is expressed by Equation 4, as follows:

$\begin{matrix}{{\alpha\;{z( Y_{1} )}} = {\frac{\mathbb{d}( {{Vz}( Y_{1} )} )}{\mathbb{d}t} = {{- 4}\;\pi^{2}\;{f^{2} \cdot A \cdot {\cos( {\omega\; t} )}}}}} & (4)\end{matrix}$Therefore, the dust 180 adhering at point Y₁ receives the accelerationof Equation 4. The inertial force Fk the dust 180 receives at this timeis given by Equation 5, as follows:Fk=αz(Y ₁)·M=−4π² f ² ·A·cos(ωt)·M  (5)where M is the mass of the dust 180.

As can be seen from Equation 5, the inertial force Fk increases asfrequency f is raised, in proportion to the square of f. However, theinertial force cannot be increased if amplitude A is small, no matterhow much frequency f is raised. Generally, kinetic energy of vibrationcan be produced, but in a limited value, if the piezoelectric element120 that produces the kinetic energy has the same size. Therefore, ifthe frequency is raise in the same vibrational mode, vibrationalamplitude A will change in inverse proportion to the square of frequencyf. Even if the resonance frequency is raised to achieve a higher-orderresonance mode, the vibrational frequency will fall, not increasing thevibration speed or the vibration acceleration. Rather, if the frequencyis raised, ideal resonance will hardly be accomplished, and the loss ofvibrational energy will increase, inevitably decreasing the vibrationacceleration. That is, the mode cannot attain large amplitude if thevibration is produced in a resonance mode that uses high frequency only.The dust removal efficiency will be much impaired.

Although the dust filter 119 is rectangular, in the vibrational modes ofthe embodiment, which is shown in FIG. 4A and FIG. 5A, the peak ridgesof vibrational amplitude form curves surrounding the midpoint of eachside. The wave reflected from the side extending in the X-direction andthe wave reflected from the side extending in the Y-direction areefficiently synthesized, forming a standing wave. In the vibrationalmodes, the dust filter 119 can undergo vibration of amplitude a similarto that of concentric vibration that may occur if the dust filter 119has a disc shape. In any vibrational mode in which the amplitude issimply parallel to the side, the vibration acceleration is only 10% ormore of the acceleration achieved in this embodiment.

In the vibrational modes, the vibrational amplitude is the largest atthe center of the vibrator 170 and small at the curve at circumferentialedges. Thus, the dust removal capability is maximal at the center of theimage. If the center of the vibrator 170 is aligned with the opticalaxis, the shadow of dust 180 will not appear in the center part of theimage, which has high image quality. This is an advantage.

In the vibration node areas 173, which exist in the focusing-beampassing area 149, the nodes 178 may be changed in position by changingthe drive frequencies of the piezoelectric element 120. Then, theelement 120 resonates in a different vibrational mode, whereby the dustcan be removed, of course.

The prescribed frequency at which to vibrate the piezoelectric element120 is determined by the shape and dimensions of the dust filter 119 andpiezoelectric element 120 forming the oscillator 170, and the materialsand supported states of them. Therefore, it is desirable to measure thetemperature of the vibrator 170 and to consider the change in thenatural frequency of the vibrator 170, before the vibrator 170 is used.A temperature sensor (not shown) is therefore connected to a temperaturemeasuring circuit (not shown), in the digital camera 10. The value bywhich to correct the vibrational frequency of the vibrator 170 inaccordance with the temperature detected by the temperature sensor isstored in the nonvolatile memory 128. Then, the measured temperature andthe correction value are read into the Bucom 101. The Bucom 101calculates a drive frequency, which is used as drive frequency of thedust filter control circuit 121. Thus, vibration can be produced, whichis efficient with respect to temperature changes, as well.

The dust filter control circuit 121 of the digital camera 10 accordingto this invention will be described below, with reference to FIGS. 8 and9. The dust filter control circuit 121 has such a configuration as shownin FIG. 8. The components of the dust filter control circuit 121 producesignals (Sig1 to Sig4) of such waveforms as shown in the timing chart ofFIG. 9. These signals will control the dust filter 119, as will bedescribed below.

More specifically, as shown in FIG. 8, the dust filter control circuit121 comprises a N-scale counter 183, a half-frequency dividing circuit184, an inverter 185, a plurality of MOS transistors Q₀₀, Q₀₁ and Q₀₂, atransformer 186, and a resistor R₀₀.

The dust filter control circuit 121 is so configured that a signal(Sig4) of the prescribed frequency is produced at the secondary windingof the transformer 186 when MOS transistors Q₀₁ and Q₀₂ connected to theprimary winding of the transformer 186 are turned on and off. The signalof the prescribed frequency drives the piezoelectric element 120,thereby causing the vibrator 170, to which the dust filter 119 issecured, to produce a resonance standing wave.

The Bucom 101 has two output ports P_PwCont and D_NCnt provided ascontrol ports, and a clock generator 187. The output ports P_PwCont andD_NCnt and the clock generator 187 cooperate to control the dust filtercontrol circuit 121 as follows. The clock generator 187 outputs a pulsesignal (basic clock signal) having a frequency much higher than thefrequency of the signal that will be supplied to the piezoelectricelement 120. This output signal is signal Sig1 that has the waveformshown in the timing chart of FIG. 9. The basic clock signal is input tothe N-scale counter 183.

The N-scale counter 183 counts the pulses of the pulse signal. Everytime the count reaches a prescribed value “N,” the N-scale counter 183produces a count-end pulse signal. Thus, the basic clock signal isfrequency-divided by N. The signal the N-scale counter 183 outputs issignal Sig2 that has the waveform shown in the timing chart of FIG. 9.

The pulse signal produced by means of frequency division does not have aduty ratio of 1:1. The pulse signal is supplied to the half-frequencydividing circuit 184. The half-frequency dividing circuit 184 changesthe duty ratio of the pulse signal to 1:1. The pulse signal, thuschanged in terms of duty ratio, corresponds to signal Sig3 that has thewaveform shown in the timing chart of FIG. 9.

While the pulse signal, thus changed in duty ratio, is high, MOStransistor Q₀₁ to which this signal has been input is turned on. In themeantime, the pulse signal is supplied via the inverter 185 to MOStransistor Q₀₂. Therefore, while the pulse signal (signal Sig3) is lowstate, MOS transistor Q₀₂ to which this signal has been input is turnedon. Thus, the transistors Q₀₁ and Q₀₂, both connected to the primarywinding of the transformer 186, are alternately turned on. As a result,a signal Sig4 of such frequency as shown in FIG. 9 is produced in thesecondary winding of the transformer 186.

The winding ratio of the transformer 186 is determined by the outputvoltage of the power-supply circuit 135 and the voltage needed to drivethe piezoelectric element 120. Note that the resistor R₀₀ is provided toprevent an excessive current from flowing in the transformer 186.

In order to drive the piezoelectric element 120, MOS transistor Q₀₀ mustbe on, and a voltage must be applied from the power-supply circuit 135to the center tap of the transformer 186. In this case, MOS transistorQ₀₀ is turned on or off via the output port P_PwCont of the Bucom 101.Value “N” can be set to the N-scale counter 183 from the output portD_NCnt of the Bucom 101. Thus, the Bucom 101 can change the drivefrequency for the piezoelectric element 120, by appropriatelycontrolling value “N.”

The frequency can be calculated by using Equation 6, as follows:

$\begin{matrix}{{fdrv} = \frac{fpls}{2N}} & (6)\end{matrix}$where N is the value set to the N-scale counter 183, fpls is thefrequency of the pulse output from the clock generator 187, and fdrv isthe frequency of the signal supplied to the piezoelectric element 120.

The calculation based on Equation 6 is performed by the CPU (controlunit) of the Bucom 101.

If the dust filter 119 is vibrated at a frequency in the ultrasonicregion (i.e., 20 kHz or more), the operating state of the dust filter119 cannot be aurally discriminated, because most people cannot hearsound falling outside the range of about 20 to 20,000 Hz. This is whythe operation display LCD 129 or the operation display LED 130 has adisplay unit for showing how the dust filter 119 is operating, to theoperator of the digital camera 10. More precisely, in the digital camera10, the vibrating members (piezoelectric element 120) imparts vibrationto the dust-screening member (dust filter 119) that is arranged in frontof the CCD 117, can be vibrated and can transmit light. In the digitalcamera 10, the display unit is operated in interlock with the vibratingmember drive circuit (i.e., dust filter control circuit 121), thusinforming how the dust filter 119 is operating (later described indetail).

To explain the above-described characteristics in detail, the controlthe Bucom 101 performs will be described with reference to FIGS. 10A to14. FIGS. 10A and 10B show the flowchart that relates to the controlprogram, which the Bucom 101 starts executing when the power switch (notshown) provided on the body unit 100 of the camera 10 is turned on.

First, a process is performed to activate the digital camera 10 (StepS101). That is, the Bucom 101 controls the power-supply circuit 135. Socontrolled, the power-supply circuit 135 supplies power to the othercircuit units of the digital camera 10. Further, the Bucom 101initializes the circuit components.

Next, the Bucom 101 calls a sub-routine “silent vibration,” vibratingthe dust filter 119, making no sound (that is, at a frequency fallingoutside the audible range) (Step S102). The “audible range” ranges fromabout 200 to 20,000 Hz, because most people can hear sound fallingwithin this range.

Steps S103 to S124, which follow, make a group of steps that iscyclically repeated. That is, the Bucom 101 first detects whether anaccessory has been attached to, or detached from, the digital camera 10(Step S103). Whether the lens unit 200 (i.e., one of accessories), forexample, has been attached to the body unit 100 is detected. Thisdetection, e.g., attaching or detaching of the lens unit 200, isperformed as the Bucom 101 communicates with the Lucom 201.

If a specific accessory is detected to have been attached to the bodyunit 100 (YES in Step S104), the Bucom 101 calls a subroutine “silentvibration” and causes the dust filter 119 to vibrate silently (StepS105).

While an accessory, particularly the lens unit 200, remains not attachedto the body unit 100 that is the camera body, dust is likely to adhereto each lens, the dust filter 119, and the like. It is thereforedesirable to perform an operation of removing dust at the time when itis detected that the lens unit 200 is attached to the body unit 100. Itis highly possible that dust adheres as the outer air circulates in thebody unit 100 at the time a lens is exchanged with another. It istherefore advisable to remove dust when a lens is exchange with another.Then, it is determined that photography will be immediately performed,and the operation goes to Step S106.

If a specific accessory is not detected to have been attached to thebody unit 100 (NO in Step S104), the Bucom 101 goes to the next step,i.e., Step S106.

In Step S106, the Bucom 101 detects the state of a specific operationswitch that the digital camera 10 has.

That is, the Bucom 101 determines whether the first release switch (notshown), which is a release switch, has been operated from the on/offstate of the switch (Step S107). The Bucom 101 reads the state. If thefirst release switch has not been turned on for a predetermined time,the Bucom 101 discriminates the state of the power switch (Step S108).If the power switch is on, the Bucom 101 returns to Step S103. If thepower switch is off, the Bucom 101 performs an end-operation (e.g.,sleep).

On the other hand, the first release switch may be found to have beenturned on in Step S107. In this case, the Bucom 101 acquires theluminance data about the object from the acquired image from the imageprocess controller 126, and calculates from this data an exposure time(Tv value) and a diaphragm value (Av value) that are optimal for theimage acquisition unit 116 and lens unit 200, respectively (Step S109).

Thereafter, the Bucom 101 detects the contrast of the acquired image(step S110). The Bucom 101 then determines whether the detected contrastfalls within a tolerance range (step S111). If the contrast does notfall within the tolerance range, the Bucom 101 drives the photographiclens 202 (step S112) and returns to step S103.

On the other hand, the contrast may falls within the tolerance range. Inthis case, the Bucom 101 calls the subroutine “silent vibration” andcauses the dust filter 119 to vibrate silently (step S113).

Further, the Bucom 101 determines whether the second release switch (notshown), which is another release switch, has been operated (Step S114).If the second release switch is on, the Bucom 101 goes to Step S115 andstarts the prescribed photographic operation (later described indetail). If the second release switch is off, the Bucom 101 returns toStep S108.

During the image acquisition operation, the electronic image acquisitionis controlled for a time that corresponds to the preset time forexposure (i.e., exposure time), as in ordinary photography.

As the above-mentioned photographic operation, Steps S115 to S121 areperformed in a prescribed order to photograph an object. First, theBucom 101 transmits the Av value to the Lucom 201, instructing the Lucom201 to drive the diaphragm 203 (Step S115). Then, the Bucom 101 causesthe front curtain of the shutter 108 to start running, performing opencontrol (Step S117). Further, the Bucom 101 makes the image processcontroller 126 perform “image acquisition operation” (Step S118). Whenthe exposure to the CCD 117 (i.e., photography) for the timecorresponding to the Tv value ends, the Bucom 101 causes the rearcurtain of the shutter 108 to start running, achieving CLOSE control(Step S119). Then, the Bucom 101 cocks the shutter 108 (Step S120).

Then, the Bucom 101 instructs the Lucom 210 to move the diaphragm 203back to the open position (Step S121). Thus, a sequence of imageacquisition steps is terminated.

Next, the Bucom 101 determines whether the recording medium 127 isattached to the body unit 100 (Step S122). If the recording medium 127is not attached, the Bucom 101 displays an alarm (Step S123). The Bucom101 then returns to Step S103 and repeats a similar sequence of steps.

If the recording medium 127 is attached, the Bucom 101 instructs theimage process controller 126 to record the image data acquired byphotography, in the recording medium 127 (Step S124). When the imagedata is completely recorded, the Bucom 101 returns to Step S103 againand repeats a similar sequence of steps.

In regard to the detailed relation between the vibration state and thedisplaying state will be explained in detail, the sequence ofcontrolling the “silent vibration” subroutine will be explained withreference to FIGS. 11 to 14. The term “vibration state” means the stateof the vibration induced by the piezoelectric element 120, i.e.,vibrating members. FIG. 15 shows the form of a resonance-frequency wavethat is continuously supplied to the vibrating members during silentvibration. The subroutine of FIG. 11, i.e., “silent vibration,” and thesubroutine of FIGS. 12 to 14, i.e., “display process” are routines foraccomplishing vibration exclusively for removing dust from the dustfilter 119. Vibrational frequency f₀ is set to a value close to theresonance frequency of the dust filter 119. In the vibrational mode ofFIG. 4A, for example, the vibrational frequency is 90 kHz, higher thanat least 20 kHz, and produces sound not audible to the user.

As shown in FIG. 11, when the “silent vibration” is called, the Bucom101 first reads the data representing the drive time (Toscf0) and drivefrequency (resonance frequency: Noscf0) from the data stored in aspecific area of the nonvolatile memory 128 (Step S201). At this timing,the Bucom 101 causes the display unit provided in the operation displayLCD 129 or operation display LED 130 to turn on the vibrational modedisplay, as shown in FIG. 12 (Step S301). The Bucom 101 then determineswhether a predetermined time has passed (Step S302). If thepredetermined time has not passed, the Bucom 101 makes the display unitkeep turning on the vibrational mode display. Upon lapse of thepredetermined time, the Bucom 101 turns off the displaying of thevibrational mode display (Step S303).

Next, the Bucom 101 outputs the drive frequency Noscf0 from the outputport D_NCnt to the N-scale counter 183 of the dust filter controlcircuit 121 (Step S202).

In the following steps S203 to S205, the dust is removed as will bedescribed below. First, the Bucom 101 sets the output port P_PwCont toHigh, thereby starting the dust removal (Step S203). At this timing, theBucom 101 starts displaying the vibrating operation as shown in FIG. 13(Step S311). The Bucom 101 then determines whether or not thepredetermined time has passed (Step S312). If the predetermined time hasnot passed, the Bucom 101 keeps displaying the vibrating operation. Uponlapse of the predetermined time, the Bucom 101 stops displaying of thevibrating operation (Step S313). The display of the vibrating operation,at this time, changes as the time passes or as the dust is removed (howit changes is not shown, though). The predetermined time is almost equalto Toscf0, i.e., the time for which the vibration (later described)continues.

If the output port P_PwCont is set to High in Step S203, thepiezoelectric element 120 vibrates the dust filter 119 at the prescribedvibrational frequency (Noscf0), removing the dust 180 from the surfaceof the dust filter 119. At the same time the dust 180 is removed fromthe surface of the dust filter 119, air is vibrated, producing anultrasonic wave. The vibration at the drive frequency Noscf0, however,does not make sound audible to most people. Hence, the user hearsnothing. The Bucom 101 waits for the predetermined time Toscf0, whilethe dust filter 119 remains vibrated (Step S204). Upon lapse of thepredetermined time Toscf0, the Bucom 101 sets the output port P_PwContto Low, stopping the dust removal operation (Step S205). At this timing,the Bucom 101 turns on the display unit, whereby the displaying of thevibration-end display is turned on (Step S321). When the Bucom 101determines (in Step S322) that the predetermined time has passed, thedisplaying of the vibration-end display is turned off (Step S323). TheBucom 101 then returns to the step next to the step in which the “silentvibration” is called.

The vibrational frequency f₀ (i.e., resonance frequency Noscf0) and thedrive time (Toscf0) used in this subroutine define such a waveform asshown in the graph of FIG. 15. As can be seen from this waveform,constant vibration (f₀=90 kHz) continues for a time (i.e., Toscf0) thatis long enough to accomplish the dust removal.

That is, the vibrational mode adjusts the resonance frequency applied tothe vibrating member, controlling the dust removal.

Second Embodiment

The subroutine “silent vibration” called in the camera sequence (mainroutine) that the Bucom performs in a digital camera that is a secondembodiment of the image equipment according to this invention will bedescribed with reference to FIG. 16. FIG. 16 illustrates a modificationof the subroutine “silent vibration” shown in FIG. 11. The secondembodiment differs from the first embodiment in the operating mode ofthe dust filter 119. In the first embodiment, the dust filter 119 isdriven at a fixed frequency, i.e., frequency f₀, producing a standingwave. By contrast, in the second embodiment, the drive frequency isgradually changed, thereby achieving large-amplitude vibration atvarious frequencies including the resonance frequency, without strictlycontrolling the drive frequency.

Moreover, in the dust filter 119, there is an aspect ratio that thevibrational mode will greatly change (that is, the vibration speed ratiowill abruptly change) if the aspect ratio changes in the dust filter 119owing to fluctuations during the manufacture. Therefore, in the case ofthe dust filter 119 in which such an aspect ratio is present, it isnecessary to set a precise resonance frequency in each product and todrive the piezoelectric element 120 at the frequency. This is becausethe vibration speed further lowers, if the piezoelectric element isdriven at any frequency other than the resonance frequency. An extremelysimple control circuit configuration can, nonetheless, drive thepiezoelectric element precisely at the resonance frequency if thefrequency is controlled as in the second embodiment. A method of controlcan therefore be achieved to eliminate any difference in resonancefrequency between the products.

First, the Bucom 101 reads the data representing the drive time(Toscf0), drive-start frequency (Noscfs), frequency change value (Δf)and drive-end frequency (Noscft), from the data stored in a specificarea of the nonvolatile memory 128 (Step S211). At this timing, theBucom 101 causes the display unit to display the vibrational mode asshown in FIG. 12, in the same way as in the first embodiment.

Next, the Bucom 101 sets the drive-start frequency (Noscfs) as drivefrequency (Noscf) (Step S212). The Bucom 101 then outputs the drivefrequency (Noscf) from the output port D_NCnt to the N-scale counter 183of the dust filter control circuit 121 (Step S213).

In the following steps S214 et seq., the dust is removed as will bedescribed below. First, the dust removal is started. At this time, thedisplay of the vibrating operation is performed as shown in FIG. 13, asin the first embodiment.

First, the Bucom 101 sets the output port P_PwCont to High, to achievedust removal (Step S214). The piezoelectric element 120 vibrates thedust filter 119 at the prescribed vibrational frequency (Noscf),producing a standing wave of a small amplitude at the dust filter 119.The dust 180 cannot be removed from the surface of the dust filter 119,because the vibrational amplitude is small. This vibration continues forthe drive time (Toscf0) (Step S215). Upon lapse of this drive time(Toscf0), the Bucom 101 determines whether the drive frequency (Noscf)is equal to the drive-end frequency (Noscft) (Step S216). If the drivefrequency is not equal to the drive-end frequency (NO in Step S216), theBucom 101 adds the frequency change value (Δf) to the drive frequency(Noscf), and sets the sum to the drive frequency (Noscf) (Step S217).Then, the Bucom 101 repeats the sequence of Steps S212 to S216.

If the drive frequency (Noscf) is equal to the drive-end frequency(Noscft) (YES in Step S216), the Bucom 101 sets the output port P_PwContto Low, stopping the vibration of the piezoelectric element 120 (StepS218), thereby terminating the “silent vibration.” At this point, thedisplay of vibration-end is performed as shown in FIG. 14, as in thefirst embodiment.

As the frequency is gradually changed as described above, the amplitudeof the standing wave increases. In view of this, the drive-startfrequency (Noscfs), the frequency change value (Δf) and the drive-endfrequency (Noscft) are set so that the resonance frequency of thestanding wave may be surpassed. As a result, a standing wave of smallvibrational amplitude is produced at the dust filter 119. The standingwave can thereby controlled, such that its vibrational amplitudegradually increases until it becomes resonance vibration, and thendecreases thereafter. If the vibrational amplitude (corresponding tovibration speed) is larger than a prescribed value, the dust 180 can beremoved. In other words, the dust 180 can be removed while thevibrational frequency remains in a prescribed range. This range is broadin the present embodiment, because the vibrational amplitude is largeduring the resonance.

If the difference between the drive-start frequency (Noscfs) and thedrive-end frequency (Noscft) is large, the fluctuation of the resonancefrequency, due to the temperature of the vibrator 170 or to thedeviation in characteristic change of the vibrator 170, during themanufacture, can be absorbed. Hence, the dust 180 can be reliablyremoved from the dust filter 119, by using an extremely simple circuitconfiguration.

The present invention has been explained, describing some embodiments.Nonetheless, this invention is not limited to the embodiments describedabove. Various changes and modifications can, of course, be made withinthe scope and spirit of the invention.

For example, a mechanism that applies an air flow or a mechanism thathas a wipe may be used in combination with the dust removal mechanismhaving the vibrating member, in order to remove the dust 180 from thedust filter 119.

Moreover, in the above embodiments, a liquid crystal monitor is used aviewfinder. It is of course also possible to use a single-lens reflexcamera having an optical viewfinder.

In the embodiments described above, the CCD 117 is used as an imagesensor element. It is of course permitted to use a CMOS and other imagesensor. Further, in the embodiments, the vibrating member ispiezoelectric element 120. The piezoelectric element may be replaced byelectrostrictive member or super nagnetostrictive element.

In order to remove dust 180 more efficiently from the member vibrated,the member may be coated with an indium-tin oxide (ITO) film, which is atransparent conductive film, indium-zinc film, poly 3,4-ethylenedioxythiophene film, surfactant agent film that is a hygroscopicanti-electrostatic film, siloxane-based film, or the like. In this case,the frequency, the drive time, etc., all related to the vibration, areset to values that accord with the material of the film.

Moreover, the optical LPF 118, described as one embodiment of theinvention, may be replaced by a plurality of optical LPFs that exhibitbirefringence. Of these optical LPFs, the optical LPF located closest tothe object of photography may be used as a dust-screening member (i.e.,a subject to be vibrated), in place of the dust filter 119 shown in FIG.2A.

Further, a camera may does not have the optical LPF 118 of FIG. 2Adescribed as one embodiment of the invention, and the dust filter 119may be used as an optical element such as an optical LPF, aninfrared-beam filter, a deflection filter, or a half mirror.

Furthermore, the camera may not have the optical LPF 118, and the dustfilter 119 may be replaced by the protection glass plate 142 shown inFIG. 2A. In this case, the protection glass plate 142 and the CCD chip136 remain free of dust and moisture, and the structure of FIG. 2A thatsupports and yet vibrates the dust filter 119 may be used to support andvibrate the protection glass plate 142. Needless to say, the protectionglass plate 142 may be used as an optical element such as an opticalLPF, an infrared-beam filter, a deflection filter, or a half mirror.

The image equipment according to this invention is not limited to theimage acquisition apparatus (digital camera) exemplified above. Thisinvention can be applied to any other apparatus that needs a dustremoval function. The invention can be practiced in the form of variousmodifications, if necessary. More specifically, a dust moving mechanismaccording to this invention may be arranged between the display elementand the light source or image projecting lens in an image projector.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A vibrating device comprising: a holding memberconfigured to hold an image forming element having an image surface inwhich an optical image is generated; a dust-screening member including aplate-like light transmitting portion which has a polygonal shapeincluding a plurality of sides and is configured to permit thetransmission of one of light coming from the image forming element andlight coming into the image forming element, and at least one plate-likeside wall portion which tilts as much as a predetermined angle andextends from at least one side of the plate-like light transmittingportion; and a vibrating member fixed to one plate-like side wallportion among the at least one plate-like side wall portion andconfigured to apply a vertical vibrational amplitude to the surface ofthe plate-like light transmitting portion, wherein the plate-like lighttransmitting portion and the at least one plate-like side wall portionare formed to have a substantially uniform thickness by use of the samematerial, the plate-like light transmitting portion is positioned infront of the image forming element, the one plate-like side wall portionprovided with the vibrating member is fixed to the holding member at aposition other than a position to which the vibrating member is fixed,in the polygonal shape forming the light transmitting portion, a sidewall portion does not extend from at least sides of both sides adjacentto a side from which the plate-shape side wall extends, and thedust-screening member is fixed to the holding member at a position otherthan a portion to which the vibrating member is fixed.
 2. The deviceaccording to claim 1, wherein an elastic member is interposed betweenthe plate-like light transmitting portion and the holding member, andone side of the plate-like light transmitting portion from which theplate-like side wall portion does not extend forms a free end.
 3. Thedevice according to claim 1, wherein the plate-like side wall portionhas a rectangular shape formed by one side of the plate-like lighttransmitting portion and a side which is shorter than the one side ofthe plate-like light transmitting portion.
 4. The device according toclaim 3, wherein the vibrating member has a rectangular shape, and thevibrating member is arranged to be received in the one plate-like sidewall portion.
 5. The device according to claim 1, wherein one side ofthe vibrating member in a longitudinal direction thereof is arrangedsubstantially in parallel with the one side of the plate-like lighttransmitting portion, and a first virtual axis connecting a midpoint ofthe one side of the vibrating member in the longitudinal directionthereof to a midpoint of the one side of the plate-like lighttransmitting portion matches a second virtual axis connecting avibration center of the plate-like light transmitting portion to themidpoint of the one side of the plate-like light transmitting portion.6. The device according to claim 1, wherein the plate-like lighttransmitting portion has a rectangular shape, the plate-like side wallportions extend respectively from one of sides, which face each other,of the plate-like transmitting portion, and the dust-screening memberhas a U-shape as a whole.
 7. The device according to claim 1, whereinthe plate-like side wall portion tilts in a range of 0 to 135.degree,with respect to an extension line of the light transmitting portion. 8.The device according to claim 1, wherein the side wall portion providedwith the vibrating member is fixed to the holding member at a portion inthe side wall portion other than a portion to which the vibrating memberis fixed.
 9. An image equipment comprising: an image forming elementhaving an image surface in which an optical image is generated; aholding member configured to hold the image forming element; adust-screening member including a plate-like light transmitting portionwhich has a polygonal shape including a plurality of sides and isconfigured to permit the transmission of one of light coming from theimage forming element and light coming into the image forming element,and at least one plate-like side wall portion which tilts as much as apredetermined angle and extends from at least one side of the plate-likelight transmitting portion so that they do not come in contact with eachother; and a vibrating member fixed to one plate-like side wall portionamong the at least one plate-like side wall portion and configured toapply a vertical vibrational amplitude to the surface of the plate-likelight transmitting portion, wherein the plate-like light transmittingportion and the at least one plate-like side wall portion are formed tohave a substantially uniform thickness by use of the same material, theplate-like light transmitting portion is positioned in front of theimage forming element, the one plate-like side wall portion providedwith the vibrating member is fixed to the holding member at a positionother than a position to which the vibrating member is fixed, in thepolygonal shape forming the light transmitting portion, a side wallportion does not extend from at least sides of both sides adjacent to aside from which the plate-shape side wall extends, and the dustscreening member is fixed to the holding member at a position other thana portion to which the vibrating member is fixed.
 10. The equipmentaccording to claim 9, wherein the side wall portion provided with thevibrating member is fixed to the holding member at a portion in the sidewall portion other than a portion to which the vibrating member isfixed.